Refrigerating apparatus



Filed Jan. 6. 1956 INVENTOR. J/mns mncoas HIS ATM/Mi Y United States REFRIGERATIN G APPARATUS Application January 6, 1956, Serial No. 557,696

5 Claims. (Cl. 62-155) This invention relates to refrigerating apparatus and more particularly to an arrangement for defrosting the freezer compartment evaporator in a two-temperature refrigerator.

It is an object of this invention to provide a simple and practical two-temperature refrigerating system wherein the evaporator in the high temperature food storage compartment is defrosted at relatively frequent intervals and the evaporator for the low temperature compartment is defrosted at less frequent intervals.

Another object of this invention is to provide a refrigerating system in which hot gas is fed into the low temperature evaporator for defrosting the same in such a quantity and manner that any hot gas which may condense therein will be re-evaporated before returning to the compressor.

Still another object of this invention is to provide a refrigerating system wherein hot gas is fed from the condenser into the evaporator for defrosting the evaporator and wherein a means is provided for insuring high head pressure in the condenser immediately preceding the defrosting operation.

Still another object of this invention is to provide an improved arrangement for timing the frequency of the defrost operation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

The sole figure in the drawing somewhat diagrammatically illustrates the refrigerant circuit as well as the electrical controls for use in automatically defrosting a two-temperature refrigerator.

Referring now to the drawing, wherein a preferred embodiment of the invention has been shown, reference numeral generally designates a conventional insulated refrigerator cabinet having a frozen food storage compartment 12 located in the upper part thereof and a relatively high temperature food storage compartment 14 located directly below but insulated from the freezer compartment 12. A machinery compartment 16 is located beneath the compartment 14, as shown.

The refrigerating system is of the general type shown in U.S. Patent No. 2,672,020 except for certain differences to be more fully outlined hereinafter. Thus, the refrigerating system includes a conventional sealed motorcompressor unit 18 having its outlet connected to the usual super heat removing coil 22 which returns the compressed refrigerant to the outer housing for the motor-compressor unit 18 in accordance with wellknown practice. In returning the compressed gas to the housing of the motor-compressor unit 18, any entrained lubricant vapor has a chance to settle out from the refrigerant vapor before the refrigerant flows into atent O the condenser 24 through the line 26, in accordance with conventional practice.

During the refrigeration cycle, the compressed refrigerant condenses in the condenser 24 and is fed through a fixed restrictor 26 into a low temperature evaporator 28 which surrounds the frozen food compartment 12 so as to maintain the compartment 12 at a temperature of approximately 0 or lower. The amount of liquid refrigerant fed into the evaporator 28 is more than enough to maintain the frozen food compartment refrigerated and as a result thereof, a portion of the refrigerant is fed into the accumulator or disengaging chamber 30 which may be formed within one wall of the compartment 12, such as the back wall, as shown. The preferred arrangement is to use an accumulator of the roll bonded waflle plate type so as to conserve space and at the same time provide a fairly large and effective disengaging chamber. Liquid refrigerant leaves the chamber 30 through a line 32 which leads to the platetype evaporator 34 located in the higher temperature food storage compartment 14. The plate-type evaporator 34 is provided with an accumulator or disengaging chamber 36 of the waflle design at the outlet thereof, as shown.

During normal operation of the apparatus thus far described, the frozen food storage compartment 12 is maintained at a low enough temperature to store frozen foods, whereas the compartment 14 is maintained at a temperature of approximately 36 for the purpose of preserving unfrozen foods. A thermostat 40 located on the plate evaporator 34 normally cycles the motor-compressor unit 18 by opening and closing the main motor control switch 42. This thermostatic control is of the type which closes the switch 42 whenever the temperature of the plate evaporator 34 exceeds 34 F. and maintains the circuit to the compressor closed until the temperature of the evaporator 34 falls to approximately 2 F. at which time the motor-compressor unit stops operating until the evaporator 34 has been defrosted. The thermostat 40 and the switch 42 very efiectively serve to control the operation of the refrigeration system so as to defrost the plate evaporator 34 during each oif cycle without causing any defrosting of the frozen food storage evaporator 28.

Only a relatively small amount of frost tends to accumulate on the lower temperature evaporator 28 and consequently, it is not necessary or desirable to defrost this evaporator each time the evaporator 34 is defrosted. The amount of ice which accumulates is determined to a large extent by the amount of ice that is frozen within the compartment 12 and the frequency at which the doors to the food compartment are opened. The above factors also determine to a large extent the portion of the time during which the motor-compressor unit 18 is required to operate and consequently, the timer 50 which has been provided for timing the defrost cycle for the frozen food compartment 28 is so connected in the circuit that it will only count the time during which the motor-compressor unit 18 operates. Thus, the timer motor 50 includes a field winding 52 which is arranged as shown in series with the switch 42 across the power supply line 54. The timer motor 50 is provided with a driven cam 54 which serves to actuate a switch operating plunger 56, as shown. The plunger 56 is adapted to ride on the cam 54 and does not close any circuits until the cam follower 56 rides up onto the cam surface 58 at which time a circuit is closed at the contacts 60. Closing of the circuit through the contacts 60 short-circuits the thermostatically operated switch 42 whereby the motor-compressor unit 18 will serve to operate even though the thermostat 40 may indicate that no refrigeration is required. The purpose of this is to build up the head pressure in the condenser 24 just prior to the defrosting of the evaporator 28.

The cam 54 is provided with a second raised portion 62 which subsequently serves to raise the cam follower high enough to close a circuit through the contacts 64. When the contacts 64 are closed, current is fed to the solenoid operated valve 66 located in a bypass line 68 which is arranged as shown. Upon opening of the valve 66 hot uncondensed refrigerant vapor contained in the motor-compressor housing 18, the super heat removing coil 22, and the condenser 24 is free to flow upwardly through the bypass line 68 into the evaporator 28. The condensed liquid in the condenser 24 goes through a phase change because of the sudden lowering of the vapor pressure upon it. Thus, the liquid in the condenser boils and the condenser 24 becomes a high temperature evaporator. The vapor in the condenser then passes up the bypass line 68 into the freezing compartment evaporator 28. This quantity of vapor which is fed through the line 68 into the evaporator 28 for defrost purposes is in excess of that actually required to defrost the evaporator whereby the refrigerant vapor which has been condensed in the evaporator 28 during the defrost cycle is re-evaporated by such excess refrigerant prior to its return to the compressor, with the result that no slugs of refrigerant enter the compressor.

It will be noted that even though some liquid refrigerant is shoved out of the evaporator 28 by the inrushing hot gas flowing through the line 68, this refrigerant will be trapped either in the accumulator 30 or in the accumulator 36 and by virtue of the construction and arrange ment of these accumulators and the refrigerant lines connected to these accumulators, the hot gas will have a chance to vaporize any accumulated refrigerant liquid before the same will have a chance to return in liquid form to the motor-compressor unit 18.

The frequency at which the frozen food compartment evaporator 28 is defrosted is broadly immaterial insofar as certain aspects of this invention are concerned. In actual practice, this evaporator should not be defrosted more than once a day and under certain conditions, it may not be necessary to defrost the evaporator more than once every week, and possibly once or twice a month. In the system shown, the frequency of the defrost cycle for the evaporator 28 will be determined by the length of time that the motor-compressor operates in any given time interval and will also be determined by the design of the motor 50 and the cam wheel 54 driven thereby. The length of the cam surface 58 should be sufiicient to build up the head pressure in the condenser prior to the opening of the valve 66 and the length of the cam surface 62 should be great enough so as to maintain the valve 66 open long enough to defrost the evaporator 28 and to re-evaporate any of the refrigerant which may have been condensed in the evaporator 28 during the main portion of the defrost cycle.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus including an above-freezing food storage compartment and a below-freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporator means in heat exchange relation with said below-freezing compartment and having its inlet connected to an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to the outlet of said freezing evaporator means, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, a thermostatic cycling control means having a thermally sensitive element in direct intimate contact with said food compartment evaporating means having means for preventing the starting of said liquefying means until the food compartment evaporating means reaches a temperature above 32 F. for defrosting said food compartment evaporating means and having means for preventing the stopping of said liquefying means until said food compartment evaporating means is cooled to below-freezing temperatures, and means for supplying compressed refrigerant to said freezing evaporating means at defrosting temperatures so as to defrost said freezing evaporating means, and means for controlling the supply of said compressed refrigerant to said freezing evaporating means so as to cause defrosting thereof at less frequent intervals than said food compartment evaporating means is defrosted.

2. Refrigerating apparatus including an above-freezing food compartment and a below-freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporator means in heat exchange relation with said below-freezing compartment and having its inlet connected to an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to the outlet of said freezing evaporator means, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, a thermostatic cycling control means having a thermally sensitive element in direct intimate contact with said food compartment evaporating means having means for preventing the starting of said liquefying means until the food compartment evaporating means reaches a temperature above 32 F. for defrosting said food compartment evaporating means and having means for preventing the stopping of said liquefying means until said food compartment evaporating means is cooled to below-freezing temperatures, means for supplying relatively hot compressed refrigerant vapor to said freezing evaporating means so as to defrost said freezing evaporating means, means for controlling the supply of said compressed refrigerant vapor to said feezing evaporating means so as to cause defrosting thereof at less frequent intervals than said food compartment evaporating means is defrosted, and means for insuring energization of said refnigerant liquefying means for a given period of time immediately preceding the supply of compressed refrigerant vapor to said freezing evaporating means irrespective of refrigeration requirements.

3. In a two-temperature refrigerating system, a first evaporator, a second evaporator, a compressor, a condenser, means for connecting said compressor, condenser and first and second evaporator means in series refrigerant flow relationship, said means including a pressure reducing element between the outlet of said condenser and the inlet of said first evaporator, means responsive to the temperature of said second evaporator for cycling said compressor so as to operate said second evaporator on a defrosting cycle wherein said second evaporator defrosts during each oflf cycle of said compressor, means for bypassing compressed vapor from the inlet of said condenser to the inlet of said first evaporator so as to cause defrosting of said first evaporator, and mechanically controlled means for cycling the flow of refrigerant through said bypass so as to cause defrosting of said first evaporator at less frequent intervals than that at which said second evaporator is defrosted.

4. In a two-temperature refrigerating system, a first evaporator, a second evaporator, a compressor, a condenser, means for connecting said compressor, condenser and first and second evaporator means in series refrigerant fiow relationship, said means including a pressure reducing element between the outlet of said condenser and the inlet of said first evaporator, means responsive to the temperature of said second evaporator for cycling said compressor so as to operate said second evaporator on a defrosting cycle wherein said second evaporator defrosts during intervals corresponding to each ofi cycle of said compressor, means for bypassing compressed vapor from the inlet of said condenser to the inlet of said first evaporator so as to cause defrosting of said first evaporator, and mechanically controlled means for controlling said bypassing means, said last named means including means for insuring operation of said compressor for an interval of time immediately preceding the opening of said bypass means.

5. In combination, means forming a plurality of insulated compartments, a first evaporator maintaining one of said compartments at a relatively low temperature, a second evaporator maintaining the other of said compartments at a relatively higher temperature, refrigerant liquefying apparatus including a compressor and condenser, means including a pressure reducing means supplying liquid refrigerant from said condenser to said first and second evaporators in series, means for returning refrigerant vaporized in said second evaporator to said compressor, control means for said compressor including a thermostat arranged in thermal exchange relationship with said second evaporator and calibrated to cause operation of said compressor on a defrost cycle whereby said second evaporator is defrosted during each off portion of said cycle, and means for supplying refrigerant vapor at controlled intervals from the outlet of said compressor to the inlet of said first evaporator so as to defrost said first evaporator at less frequent intervals than said second evaporator is defrosted.

References Cited in the file of this patent UNITED STATES PATENTS 2,033,828 Heitman Mar. 10, 1936 2,084,730 Gill June 22, 1937 2,612,026 Hansen Sept. 30, 1952 2,672,020 Wurtz et a1. Mar. 16, 1954 2,708,348 Philipp May 17, 1955 2,736,173 Duncan Feb. 28, 1956 2,741,097 Miles Apr. 10, 1956 2,743,587 Hubacker May 1, 1956 2,745,255 Phillip May 15, 1956 2,780,925 McGrew Feb. 12, 1957 1,788,640 Newberry Apr. 16, 1957 2,800,773 Crew July 30, 1957 

